Method and apparatus for reducing noise in a communication system

ABSTRACT

A system that incorporates teachings of the present disclosure may include, for example, a controller to: determine crosstalk coupling characteristics between a plurality of lines of a Digital Subscriber Line (DSL) system connected to a plurality of modems based on a transition between a full power mode and one or more other modes, and provide the determined crosstalk coupling characteristics to one or more of the plurality of modems for performance of at least one of pre-coding a transmitted signal and processing a received signal along a line of the plurality of lines, where the pre-coding and processing is performed based at least in part on the determined crosstalk coupling characteristics, and where the pre-coding of the transmitted signal and the processing of the received signal reduce effects of fluctuating crosstalk. Other embodiments are disclosed.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to communication systems andmore specifically to a method and apparatus for reducing noise in acommunication system.

BACKGROUND

Communication systems consume large amounts of power and often employpower conservation methods. One such method is a reduced power mode ofoperation where a transmitted signal can be modified by reducing theamplitude of the signal during the times when data traffic has ceased oris relatively small. In a reduced power mode, the information providedover a connection can be limited, such as to information which isrequired to maintain a connection and synchronization between twocommunicating modems, while allowing the modems to exchange messagesnecessary to leave the low power mode and return to a normaltransmission mode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-10 depict illustrative embodiments of communication systems thatprovide network communications;

FIGS. 11-12 depict illustrative embodiments of methods operating inportions of the communication systems of FIGS. 1-10; and

FIG. 13 is a diagrammatic representation of a machine in the form of acomputer system within which a set of instructions, when executed, maycause the machine to perform any one or more of the methodologiesdiscussed herein.

DETAILED DESCRIPTION

One embodiment of the present disclosure can entail a computer-readablestorage medium having computer instructions for monitoring a pluralityof modems in a Digital Subscriber Line (DSL) system for transitioningbetween a full power mode and one or more other modes; determiningcrosstalk coupling characteristics between a plurality of lines of theDSL system connected to the plurality of modems based at least in parton changes in amplitude of transmitted signals where the amplitudechanges result from the transition between the full power mode and theone or more other modes; and providing the determined crosstalk couplingcharacteristics to one or more of the plurality of modems forperformance of at least one of pre-coding a transmitted signal andprocessing a received signal along a line of the plurality of lines,where the pre-coding and processing are performed based at least in parton the determined crosstalk coupling characteristics and temporalcharacteristics associated with the one or more other modes, and wherethe pre-coding of the transmitted signal and the processing of thereceived signal reduce effects of fluctuating crosstalk.

Another embodiment of the present disclosure can entail an apparatuscomprising a controller to: determine crosstalk coupling characteristicsbetween a plurality of lines of a Digital Subscriber Line (DSL) systemconnected to a plurality of modems; and provide the determined crosstalkcoupling characteristics to one or more of the plurality of modems forperformance of at least one of pre-coding a transmitted signal andprocessing a received signal along a line of the plurality of lines,where the pre-coding and processing are performed based at least in parton the determined crosstalk coupling characteristics, and where thepre-coding of the transmitted signal and the processing of the receivedsignal reduce effects of fluctuating crosstalk.

Yet another embodiment of the present disclosure can entail a methodincluding providing a full power mode and other modes of operation formodems in a Digital Subscriber Line (DSL) system; determining one ormore first lines of a cable that will be effected by a change in atransmitted signal amplitude of a second line of the cable, where thefirst and second lines are connected to the modems in the DSL system;providing a transition time to one or more first modems that areconnected to the first lines, where the transition time is a time when asecond modem connected to the second line transitions between at leastone of the full power mode to a second mode and the second mode to thefull power mode; and adjusting an operating mode of the one or morefirst modems in proximity to the transition time to compensate foreffects of fluctuating crosstalk.

Yet another embodiment of the present disclosure can entail a networkdevice of a Digital Subscriber Line (DSL) system, where the networkdevice comprises a controller to: transition between a full power modeand one or more other modes; receive crosstalk coupling characteristicsassociated with a plurality of lines of the DSL system, where thenetwork device is connected to a line of the plurality of lines; andperform at least one of pre-coding a signal to be transmitted andprocessing a received signal, where the pre-coding and processing areperformed based at least in part on the received crosstalk couplingcharacteristics, and where the pre-coding of the transmitted signal andthe processing of the received signal reduce effects of fluctuatingcrosstalk.

Yet another embodiment of the present disclosure can entail a methodincluding applying vectoring to one or more lines of a plurality oflines in a Digital Subscriber Line system to reduce effects offluctuating crosstalk being experienced by the plurality of lines, whereat least a portion of the plurality of lines transition between fullpower and low power modes.

Yet another embodiment of the present disclosure can entail providing aplurality of lines in a Digital Subscriber Line (DSL) system, where theplurality of lines are connected to modems, and where fluctuatingcrosstalk occurs in the plurality of lines based on at least a portionof the plurality of lines transitioning between a full power mode andone or more other modes; and applying vectoring to one or more lines ofthe plurality of lines to reduce effects of the fluctuating crosstalkbeing experienced by the plurality of lines.

FIG. 1 depicts an illustrative embodiment of a first communicationsystem 100 for providing network communication, including delivering andreceiving media content, data and so forth. The communication system 100can represent an Internet Protocol Television (IPTV) broadcast mediasystem, although various other types of network communication systemscan be realized by the system. An access network can be provided thatutilizes DSL connections (including various types such as ADSL,ADSL2plus, VDSL2, SHDSL, and so forth) with a commercial and/orresidential building 102 for providing network communication, such asbetween one or more computing devices 108 and the Internet. The accessnetwork can include various network elements for facilitating thedelivery of data, including a bank of digital subscriber line accessmultiplexers (DSLAMs) located in a central office or a service areainterface that provides broadband services over copper twisted pairs tobuildings 102.

In one embodiment, the system 100 can include an IPTV infrastructure,where there can be a super head-end office (SHO) with at least one superheadend office server (SHS) which receives national media programs fromsatellite and/or media servers from service providers of multimediabroadcast channels. In the present context, media programs can representaudio content, moving image content such as videos, still image content,and/or combinations thereof. The SHS server can forward IP packetsassociated with the media content to video head-end servers (VHS) via anetwork of aggregation points such as video head-end offices (VHO)according to a common multicast communication method.

The VHS can then distribute multimedia broadcast programs via the accessnetwork to the commercial and/or residential buildings 102 housing agateway 104 (such as a residential gateway or RG). The gateway 104 candistribute broadcast signals to media processors 106 such as Set-TopBoxes (STBs) which in turn present broadcast selections to media devices108 such as computers or television sets managed in some instances by amedia controller 107 (such as an infrared or RF remote control). Unicasttraffic can also be exchanged between the media processors 106 andsubsystems of the IPTV media system for services such as video-on-demand(VoD). It will be appreciated by one of ordinary skill in the art thatthe media devices 108 and/or portable communication devices 116 shown inFIG. 1 can be an integral part of the media processor 106 and can becommunicatively coupled to the gateway 104. In this particularembodiment, an integral device such as described can receive, respond,process and present multicast or unicast media content.

The system 100 can be coupled to one or more computing devices 130, aportion of which can operate as a web server for providing portalservices over an Internet Service Provider (ISP) network 132 to fixedline and/or wireless computing or media devices 108. Although not shown,various components of the communication system 100 can also be combinedwith or replaced by analog or digital broadcast distributions systemcomponents, such as cable TV system components.

FIG. 2 depicts an illustrative embodiment where power mode changes occurin a communication system 200. In one embodiment, the system 200 candeliver media content, although various forms of network communicationare contemplated, including data and voice. Communication system 200 canbe overlaid or operably coupled with communication system 100 as anotherrepresentative embodiment of said communication system. As shown, thesystem 200 can include a low power mode, which is the L2 powermanagement mode, that reduces the power consumed by modems for periodsof time when there is little or no traffic on the line, such asaccording to ITU-T Recommendation G.992.3 (ADSL2) and RecommendationG.992.5 (ADSL2plus). The present disclosure contemplates other powerreduction techniques, protocols or standards being followed by system200, including for other DSL technologies (such as G.993.2 for VDSL2).The normal power mode is the L0 mode, while the idle mode where the DSLconnection is not established, is the L3 mode. System 200 can include apre-coder 220, a vectoring controller 230, and L2 mode controllers 240.System 200 can reduce or eliminate the detrimental affects offluctuating crosstalk caused by toggling between the L2 and L0 modes byapplying vectoring to the respective lines as will be described againlater.

During a reduced power mode of system 200, the transmitted signal can bemodified by reducing the amplitude of the DSL signal during the timeswhen data traffic sent by applications over the DSL connection isadequately small, thereby reducing the power consumed by the modem. Forinstance, the amplitude of each of the DMT tones can be reduced,including the number of data bits transmitted per tone. In oneembodiment, the lowering of the power modes reduces the powertransmitted into the line, thus reducing overall power used by themodem.

In one embodiment, application data sent over the network in system 200may not be transmitted over the DSL connection while a transmitting anda receiving pair of modems is in L2 mode; instead the informationencoded over the DSL connection may be solely that required to keep theconnection between the two modems established and synchronized, whileallowing the modems to exchange the messages required to leave the L2mode and return to normal transmission when application data is againavailable for transmission. In another embodiment, low-bit-rateapplication data can be transmitted during the L2 mode, such as VoIPapplication data.

FIG. 3 depicts an illustrative embodiment of power reductions achievedduring the showtime state, when a modem of another communication system300 enters the L2 mode. Communication system 300 can be overlaid oroperably coupled with communication systems 100-200 as anotherrepresentative embodiment of said communication systems.

The DSL low power modes can enable a transmitting and receiving pair ofmodems supporting the DSL connection to enter and leave the mode veryquickly when data traffic is not being transmitted over the DSLconnection. The signal transmitted during the mode can keep theconnection between the two modems established and synchronized, and thesignal can return to full-power data transmission capabilities as soonas a high-bit-rate application makes such a request. Entering into thereduced power mode and leaving the mode can occur fast enough so thatthe application processes at each end of the connection dealing with thetransferred data are not affected by the transitions from the L2 modeback to the L0 normal transmission mode.

As a result of the intermittent nature of data packets to and from thecustomer, the DSL may frequently transition between the full power (L0)and low power (L2) modes. These transitions between the L0 and L2 modesmay occur as frequently as once every one or two seconds due torelatively short but frequent gaps in the user's data stream.Additionally these transitions into and out of the L2 mode can occur atvarying and unpredictable intervals based solely on the specifics natureof the communications carried over the DSL connection. The occurrence ofsuch transitions can be difficult to characterize or predict. Both ofthese characteristics of the L2/L0 transition can cause frequentfluctuations in the transmitted spectrum and signal level from a modemtransitioning between the L0 the L2 mode. These changes can occur atvarious and unpredictable times.

Crosstalk is the resulting signal coupled to other lines in the cable,which will correspondingly fluctuate with the transitions between the L0mode and the L2 mode. Receivers on the other DSL lines in a cable cansee crosstalk as noise. Fluctuating crosstalk, which is known asnon-stationary crosstalk, can be more disruptive to the decoding of thesignal by the receiving DSL Modem than constant crosstalk because it isdifficult for a receiver to adapt to the changing noise level.

FIG. 4 depicts an illustrative embodiment of another communicationsystem 400 for delivering media content. Communication system 400 can beoverlaid or operably coupled with communication systems 100-300 asanother representative embodiment of said communication systems. Asshown, the system 400 can include a plurality of transceivers 410, apre-coder 420 in communication with the transceivers, a vectorcontroller 430, L2 mode controllers 440, and a management entity 450.System 400 can reduce or eliminate the detrimental affects offluctuating crosstalk caused by toggling between the L2 and L0 modes byapplying vectoring to the respective lines. For instance, non-stationarycrosstalk caused by the power-saving L2 mode can be minimized byapplying vectoring for ADSL, ADSL2plus, VDSL2, SHDSL modems connected tothe lines in a cable.

In one embodiment, in order for the L2 mode to function, both thetransmitting and the receiving DSL modem at either the DSLAM or the CPEcan have advance knowledge of: time of entry in L2 mode and thecorresponding Power Cut-Back (PCB) increase; time of application of apotential “power-trim” while in L2 mode and the corresponding PCBadjustment; and time of exit from L2 mode and the corresponding PCBdecrease.

In another embodiment, the DSL modem can have knowledge of otherparameters such as total transmitted power, Power Spectral Density(PSD), transmit spectrum scaling coefficients, fine gains per tone, bitsper tone, and so forth, during the low-power mode and the full-powermode. In one embodiment, the knowledge is obtained by way of exchange ofinformation between the transmitting and the receiving modem through anappropriate operations channel, and/or through the use of specialsymbols (such as sync flags in G.992.3). In another embodiment, theinformation about the time of change of the power and of thecorresponding amount of change can be provided to the DSL modem modulesrelated to vectoring in order to adjust their settings at the correcttime given the expected changes.

System 400 can apply downstream vectoring for controlling crosstalk. Forexample, the Far End Crosstalk (FEXT) pre-coder 420 used in thedownstream direction on the transmitter can modify the signal so thatthe non-stationary crosstalk will be largely canceled in the receiver.For instance, when an L2-related power change is about to occur for aline, the pre-coder 420 can receive a notification from the L2 modecontroller of the corresponding line with regard to the expected time ofthe transition and the expected amount of power change.

Communication between the L2 controllers 440, the vectoring controller430, and the Management Entity 450 allows coordination between the twotypes of controllers and the Management Entity. Communications from theL2 controllers 440 to the vectoring controller 430 can include time andpower change associated with a transition event. Communication from thevectoring controller 430 to the L2 controllers 440 can allow thetransitions from the L2 mode to coordinate with the vectoring processingand, for example, can be ACK, NACK, and/or other messages such as “Notready”, “Unable to adjust to change”, and so forth. Communication fromthe L2 controllers 440 to the management entity 450 can be L2-relatedparameters, such as those already defined in the G.997.1 plus control,and reported parameters associated with L2-vectoring, such asenabling/disabling vectoring for each line, counts of the number ofevents of L2 transition events, success/failure codes, and so forth.

FIG. 5 depicts an illustrative embodiment of another communicationsystem 500 for delivering media content and in particular illustratesthe relation between the availability of application data for aparticular line, entry into L2 mode on that line and communication flowbetween two lines that utilize vectoring in the downstream direction.Communication system 500 can be overlaid or operably coupled withcommunication systems 100-400 as another representative embodiment ofsaid communication systems. System 500 includes transitions from and tothe L2 mode which is functionally represented in FIG. 5. For simplicity,FIG. 5 illustrates the situation with two lines 510, 520 and theircorresponding modems 515, 525, however it is extendable to situationswhere additional lines are vectored.

System 500 has a potential victim line 510 and a second line 520entering and leaving the L2 mode because data is periodicallyunavailable for transmission from the applications communicating overthe network. When line 510 enters the L2 mode, because there is no dataavailable from the application, it indicates to the potential victimline 510 over the interface 550 that it has entered the L2 mode. Thepre-coder function on the victim line 510 can be made aware of thecoding and PSD of the L2 mode and can adjust the pre-coding of its ownline to account for the change to the L2 mode. The pre-coding functionfor the line 520 entering and leaving the L2 mode can also modify thepre-coding of its own line to take into account the fact that the lineis in L2 mode.

In system 500, when data is available, the modem 525 can leave the L2mode and transition to the L0 normal transmission mode. The victim line510 can be notified of this change and can be provided with thecharacteristics of the PSD and signal of the line in its new state overthe interface 550 so that the victim line 510 can adjust its pre-codingto deal with the new situation. The exemplary embodiment of FIG. 5illustrates downstream vectoring for two lines 510, 520, however thepresent disclosure can be extended to situations where there areadditional lines in the vectoring group, with multiple victim lines andmultiple lines entering and leaving the L2 mode.

FIG. 6 depicts an illustrative embodiment of another communicationsystem 600 for delivering media content. Communication system 600 can beoverlaid or operably coupled with communication systems 100-500 asanother representative embodiment of said communication systems. Asshown, the system 600 can include a plurality of transceivers 610, apre-coder 620 in communication with the transceivers, a vectorcontroller 630, L2 mode controllers 640, and a management entity 650.System 600 provides for vectoring in the upstream direction to reduce oreliminate the detrimental affects of fluctuating crosstalk caused bytoggling between the L2 and L0 modes.

In the upstream direction, communication between the L2 controllers 640,the vectoring controller 630, and the management entity 650 can allowcoordination between the two types of controllers and the ManagementEntity. Communication from the L2 controllers 640 to the vectoringcontroller 630 can include time and power change associated with atransition event. Communication from the vectoring controller 630 to theL2 controllers 640 can allow the transitions from the L2 mode to becoordinated with the vectoring processing, including the use of ACK,NACK, and other messages such as “Not ready”, “Unable to adjust tochange”, and so forth. Communication from the L2 controllers 640 to themanagement entity 650 can include providing L2-related parameters, suchas those defined by the G.997.1 plus control, as well as reportedparameters associated with L2-vectoring, such as enabling/disablingvectoring for each line, counts of the number of events of L2 transitionevents, and success/failure codes, and so forth.

FIG. 7 depicts an illustrative embodiment of another communicationsystem 700 for delivering media content and in particular illustratesthe relationship between the availability of application data for aparticular line at the receiver in the upstream direction, entry into L2mode on that line and communications flows between two lines thatutilize vectoring in the upstream direction. Communication system 700can be overlaid or operably coupled with communication systems 100-600as another representative embodiment of said communication systems.System 700 includes transitions from and to the L2 mode which isfunctionally represented in FIG. 7. For simplicity, FIG. 7 illustratesthe situation with two lines 710, 720, however it is extendable tosituations where additional lines are vectored.

In one embodiment, system 700 can employ vectoring in the upstreamdirection whereby the canceling function on the receiver can cancelnon-stationary crosstalk produced by entry and exit into the L2 mode. Aline can enter (and later leave) L2 mode when there is no high-bit-rateapplication operating over the link. When that line is in L2 mode, itcan indicate to the victim line that it is in the L2 mode over theinterface 750. The first line's multi-line decoding function is able touse the fact that itself is in the L2 mode. When application data isavailable, the first modem can detect that the line is no longerreceiving the L2 mode and can transition to the L0 normal transmissionmode. The victim line 710 can be notified of this change, and thecharacteristics of the PSD and signal of the line in its new state canbe communicated to the victim line over the interface 750. The victimline 710 and the first line 720 can adjust their multi-line decodingfunctions to deal with the new situation. The exemplary embodiment ofFIG. 7 illustrates upstream vectoring for two lines, but it can beextended to situations where there are additional lines in the vectoringgroup, multiple victim lines, and/or multiple lines entering and leavingthe L2 mode.

Updating the pre-coder for upstream vectoring for an expected change inthe transmitted power can be based on equation 1:Y=H*X+N  [Eq. 1]which is applied to each DMT tone, where: Y is the received data vector;H is the MIMO channel transfer function matrix; X is the vector ofchannel inputs; and N is the channel noise vector. For the upstreamdirection, a decoding process can include:Y′=H ⁻¹ *Y=X+H ⁻¹ *N  [Eq. 2]In the case of entry or exit from L2 mode, the power of X is about tochange by a factor of A (where A is a diagonal matrix). The effect ofthis expected change in power can be undone or otherwise addressed atthe receiver as follows:Y′=H ⁻¹ *Y=A ⁻¹ *H ⁻¹*(H*A*X+N)=X+H ⁻¹ *N  [Eq. 3]Y′=A ⁻¹ *H ⁻¹ *Y=A ⁻¹ *H ⁻¹*(H*A*X+N)=X+A ⁻¹ *H ⁻¹ *N  [Eq. 4]

When using downstream vectoring, updating of the pre-coder to addressthe power change introduced by entry into L2 mode depends on whetherscaling to reduce the power in L2 mode is performed before or after thevectoring precoder operations. If L2 mode scaling is performed beforethe vectoring precoder, then it can be described as:X′=A*X″  [Eq. 5]where X″ is the mapper outputs (QAM constellation points), and A is adiagonal matrix representing the power change on entering or leaving L2mode. Pre-coding can be represented by:X=H ⁻¹ *X′  [Eq. 6]And at the receiver:Y=H*X+N=H ⁻¹ *A*X″+N=A*X″+N  [Eq. 7]

In this exemplary embodiment, the receiver can obtain samples that havebeen scaled by A. For example, the vectoring pre-coder may not need tobe adjusted simultaneously with the L2 scaling application. However, ifthe L2 mode scaling is performed after the vectoring pre-coding, thevectoring pre-coder can be updated simultaneously with the applicationof L2 scaling. For instance, if the L2 scaling is described as:X=A*X′  [Eq. 8]then the vectoring pre-coding can be expressed as:X′=B*X″  [Eq. 9]Thus, at the receiver, one obtains:Y=H*X+N=H*A*X′+N=H*A*B*X″+N  [Eq. 10]If B is chosen to be:B=A ⁻¹ *H ⁻¹ *A  [Eq. 11]then the following result is obtained:Y=A*X″+N  [Eq. 12]which means that the receiver obtains crosstalk-free samples that havebeen scaled by the diagonal matrix A, in accordance with L2 mode.

FIG. 8 depicts an illustrative embodiment of another communicationsystem 800 for delivering media content. In particular, FIG. 8 isillustrative of the reassignment of vectoring group priorities when aline enters the L2 mode. Communication system 800 can be overlaid oroperably coupled with communication systems 100-700 as anotherrepresentative embodiment of said communication systems. As shown, thesystem 800 can include lines 810 that are capable of experiencingcrosstalk, DSL modems 815 at user premises, vectoring controllers 830and L2 mode controllers 840.

In one embodiment, where a smaller vectored group consists of a subsetof lines in a cable/binder, the cancellation may not be complete. Signalprocessing speed constraints may limit cancellation to some subset ofthe lines causing crosstalk, with the preference being to cancel theworst offenders. System 800 can use information about both the L0(normal transmission mode) crosstalk and the known effects of enteringinto L2 modes on other DSL Lines, in order to select a subset of lines(the vectoring group) on which noise cancellation is to be performed.The selection can be based on optimizing the canceling of the effects ofentering and leaving L2 modes frequently.

In another embodiment, to reduce the amount of signal processing,vectoring systems can choose to cancel the crosstalk between only thosewires with the greatest crosstalk coupling, and/or only at frequencieswith the greatest crosstalk coupling. For example, system 800 can selectthe group of lines and the frequencies where vectoring would beperformed based on the knowledge of lines in L0 mode; and lines in L2mode and the associated power level.

When a first line is about to enter L2 mode, the vectoring controller830 is notified of the time of the transition and of the power change.The vectoring controller 830 can calculate if the first line willcontinue being a dominant crosstalk source after entering L2 mode. If itis estimated that the crosstalk of a second line will be greater thanthe crosstalk of the first line after entering L2 mode, then thevectoring pre-coder or de-coder can be updated to cancel the crosstalkfrom the second line, instead of from the first line. The inverseoperation may take place when the first line exits L2 mode at a latertime.

FIG. 9 depicts an illustrative embodiment of another communicationsystem 900 for delivering media content. In particular, FIG. 9illustrates the use of an L2 mode probe for determining the crosstalkcoupling within a group of mutually crosstalking lines. Communicationsystem 900 can be overlaid or operably coupled with communicationsystems 100-800 as another representative embodiment of saidcommunication systems. As shown, the system 900 can include lines 910that are capable of experiencing crosstalk, DSL modems 915 at userpremises, vectoring controller 930 and L2 mode controllers 940.

In one embodiment, where the L2 signal is well characterized, since itis different from the signal sent during normal transmission, it can besent at a time known to both the transmitter and the receiver. Inanother embodiment, the L2 signal can be used as a probe signal tofacilitate determining the crosstalk coefficients between loops in thebinder. In one embodiment, system 900 provides for vectored DSL systemslearning the crosstalk coupling characteristics between every pair ofwires in the cable. For instance, perturbations can be inserted into thetransmitted signals and then the resulting impact in thesignal-to-noise-ratio (SNR) in the other lines can be observed. Othertechniques for learning or otherwise monitoring the crosstalk couplingcharacteristics can be utilized. In one embodiment, probe signals can beutilized that specify the DMT sync symbols to be encoded in specificways that allow identification of the particular DSL service in thecable that is the source of the crosstalk received.

In one embodiment, a large change in the transmitted signal amplituderesulting from frequent transition between the full-power and low-powermodes can serve as a probing signal to determine the crosstalk couplingcharacteristics between the pairs of wires in the cable. In anotherembodiment, the signal transmitted during the L2 mode can havecharacteristics specifically intended to improve its utility as acrosstalk probe signal, such as a distinctive PSD. As the modemtransitions in and out of the low power mode, the resulting impact onSNR-vs-frequency can be observed for the modems connected to the otherwire pairs in the cable.

System 900 provides for the following flow to be utilized to provide aprobe signal for determining the crosstalk coupling between mutuallycrosstalking lines: the L2 controller 940 for each line on the accessnode can place each of the lines 2 through line N simultaneously in L2mode for a period of time where line 1 remains in the L0 Mode; when aparticular line is in L2, it can have the PSD characteristic of the L2mode and each line in L2 mode can operate at reduced power; line 1remains in L0 mode and can produce crosstalk on the other lines whichare placed in L2 mode; the ‘Vectoring Controller’ on each CPE modem 915for the lines 2 through N, which are placed in L2 mode, can analyze thesignal received and report to the access node via a control channel(such as the ‘back channel’ or ‘error channel’) information about thereceived signal specifically including deviations from signal expectedto be received if there were no crosstalk from Line 1 which is in L0mode; reports of the differences for each of the lines affected bycrosstalk from the line 1 in L0 mode can be made over the backchannel tothe vectoring controller 930 on the access node; since the vectoringcontroller is aware of the specific PSD and other characteristics ofboth the lines in L2 mode and Line 1 in L0 mode, it can use theinformation about the reported deviations in the received signal foreach line to determine the crosstalk coupled into the affected lines bythe Line 1; and/or the lines 2 through N in L2 mode can be taken out ofthe L2 mode and placed in the normal transmission of L0 mode.

This process can be repeated, in or out of sequence, for each of the Nlines, each of which can be placed in the L0 mode while all the otherlines are placed for a period of time in L2 mode and the crosstalk fromthe line remaining in L0 mode is determined. Through this iterativeprocess, the complete crosstalk coupling matrix for the entire group ofmutually crosstalking lines can be determined.

FIG. 10 depicts an illustrative embodiment of another communicationsystem 1000 for delivering media content. In particular, FIG. 10illustrates optimizing the L2 mode signal to reduce crosstalk into otherlines. Communication system 1000 can be overlaid or operably coupledwith communication systems 100-900 as another representative embodimentof said communication systems. As shown, the system 1000 can include aplurality of receivers 1010, a pre-coder 1020 in communication with thetransceivers, a vector controller 1030, L2 mode controllers 1040, and amanagement entity 1050.

When vectoring techniques are used on a line in L2 mode, the PSD andother specific attributes for the L2 state can be modified by vectoringtechniques such as pre-coding in the downstream direction or noisecancellation in the upstream relative to the L0 PSD to specificallyreduce the effects of non-stationary crosstalk into victim lines. Forexample, the vectoring controllers can ensure a choice of the details ofL2 PSD with the goal of keeping a vectoring group smaller to minimizethe computational complexity.

For example, using vectoring for full power mode, the characteristics ofthe signal sent during the full power mode can be modified to minimizethe effects of crosstalk. The specific modification to the signal can bebased on the specific crosstalk coupling determined for the other wirepairs with the greatest crosstalk coupling. In one embodiment, thecharacteristics of the signal transmitted during the low-power mode canalso be altered in a manner similar to the manner applied for vectoringduring the full-power mode. In another embodiment, the characteristicsof the signal sent during the low power mode can be modified, based onthe determined crosstalk coupling, to minimize the apparent change inthe crosstalk to the other lines in the cable that would be mostsusceptible to the crosstalk. This can result in modifying the signaltransmitted in the low-power mode to have a greater or lesser apparentcrosstalk to the other most susceptible wires. The transmittedamplitude-versus-frequency and the transmitted phase-vs-frequency can bemodified for this purpose.

In system 1000, when line 1 is placed in L2 mode by the L2 modecontroller 1040 for line 1, it can indicate to the vectoring systemcontroller 1030 that the line is to enter L2 mode. The vectoring systemcontroller 1030 can then determine the appropriate characteristics ofthe L2 signal on line 1 that will result in reduced cross-talk from line1 into the other DSL lines. The Pre-coder 1020 and other transmitfunctions for line 1 can then be configured to bring into effect thisoptimized transmit signal. In one embodiment, the vectoring systemcontroller 1030 can configure the transmit signal for line 1 in L2 modeto reduce the crosstalk effects not only into lines under control of thevectoring system controller, but also into other lines that are notunder control of the vectoring system controller. These other lines maynot be vectored to cancel the crosstalk and may still experiencecrosstalk from line 1.

In one embodiment, the system 1000 can continuously monitor the effectson SNR-vs-frequency on other lines as a line changes between thefull-power and low-power modes. In the event that the methods to cancelthe effect of crosstalk are unable to adequately eliminate the effectsof fluctuating crosstalk on other lines, the system 1000 can disable thelow-power mode for selected lines to assure the best performance forother lines.

In another embodiment, the back channel can provide ongoing monitoringabout the crosstalk introduced by other lines into a particular DSLline. This information can be combined with information, such asSNR-vs-frequency, and other information associated with the DSLconnection, such as counts of incorrectly received DMT symbols, known ascode violations or CV's, to determine if the methods to cancel theeffect of non-stationary crosstalk produced by L2 modes is adequate toensure that the DSL service is of acceptable quality. In one embodiment,if uncorrectable degradation due to L2-mode-induced non-stationarycrosstalk is detected, the L2 mode controller for a particular DSL linecan be instructed to suppress transitions into L2 mode. In this example,the modem can remain in L0 mode even in cases where application leveldata is not available for transport. Although the benefits of L2 modefor expended power savings may be lost, the effects of non-stationarycrosstalk can be avoided in this case where vectoring techniques areunable to ameliorate the effect.

FIG. 11 depicts an illustrative method 1100 operating in portions ofcommunication systems 100-1000. In particular, method 1100 describesdownstream vectoring when a L2 mode transition occurs. Method 1100begins with step 1102 in which a change in application data availabilityfor a particular line occurs. In step 1104, the L2 mode controller forthe line can receive a request for L2 mode transition. For example, therequest can include entry, power trim and/or exit information. In oneembodiment, the request can include time of transition and/or expectedpower change.

In step 1106, the L2 mode controller for the line can send informationto the vectoring controller regarding the expected transition, expectedtime, and/or expected power change. In step 1108, the vectoringcontroller can calculate new pre-coder settings based on the receivedinformation associated with the power change. The vectoring controllercan in step 1110 apply the new pre-coder settings at the expected times.In one embodiment in step 1112, the vectoring controller can sendconfirmation to the L2 mode controller. The L2 mode controller can thenapply the L2 transition at the expected time in step 1114.

FIG. 12 depicts an illustrative method 1200 operating in portions ofcommunication systems 100-1000. In particular, method 1200 describesupstream vectoring when a L2 mode transition occurs. Method 1200 beginswith step 1202 in which a change in application data availability for aparticular line occurs. The change can be observed by a signal receivedfrom a far end modem and/or at the U-C interface. In step 1204, the L2mode controller for the line can receive a request for L2 modetransition. For example, the request can include entry, power trimand/or exit information. In one embodiment, the request can include timeof transition and/or expected power change.

In step 1206, the L2 mode controller for the line can send informationto the vectoring controller regarding the expected transition, expectedtime, and/or expected power change. In step 1208, the vectoringcontroller can calculate new noise cancellation settings based on thereceived information associated with the power change. The vectoringcontroller can in step 1210 apply the new noise cancellation settings atthe expected times. In one embodiment in step 1212, the vectoringcontroller can send confirmation to the L2 mode controller. The L2 modecontroller can then apply the L2 transition at the expected time in step1214.

The exemplary embodiments can provide for the use of vectoringtechniques in the downstream direction where the transmitting modem usesthe information that it has available about the characteristics of theL2 signal, and the time of entry and exit from the L2 state inpre-coding the transmitted signal to allow the cancellation of crosstalkand minimize the detrimental affects of the non-stationary crosstalkcaused by toggling between the L2 and L0 modes. The exemplaryembodiments described herein provide for the use of vectoring techniquesin the upstream direction where the receiving modem uses the informationthat it has available about the characteristics of the L2 signal, andthe time of entry and exit from the L2 state in processing thetransmitted signal to allow the cancellation of crosstalk in thereceived signal and minimize the detrimental affects of thenon-stationary crosstalk caused by toggling between the L2 and L0 modes.

The exemplary embodiments can provide for the use of information aboutthe characteristics of the transmitted signal during L2 mode, inaddition to the L0 mode, by a DSL modem implementing vectoringtechniques to optimize the selection of the lines that are included in avectoring group where the vectoring group is made of fewer than all theDSL lines supported on a cable. The exemplary embodiments describedherein provide for the use of the DSL signal sent during L2 mode as aprobe signal to allow the determination of crosstalk coupling betweenlines in the cable in order to support vectoring techniques. However,the present disclosure contemplates the use of various techniques and/orcomponents for determining crosstalk coupling characteristics. Thesetechniques can be performed in combination with monitoring for powermode transitioning of the modems or can be performed independently ofmonitoring of the power mode transitions.

The exemplary embodiments can provide for the use of the information onthe crosstalk coupling between DSL loops in a cable to adjust thecharacteristics of the signal transmitted by a modem in the L2 mode tolessen the effect of any non-stationary crosstalk produced by entry intoL2 mode. These exemplary embodiments can be in coordination with the useof vectoring noise cancellation techniques by the modems on the lineand/or can be used independently of the implementation of vectoring bythose modems.

The exemplary embodiments can provide for the use of these techniquesfor any situation where DSL modems enter transmission states whichentail the use of characteristic PSDs and signals known to the modemssolely by the fact that they are in the state and produce non-stationarycrosstalk into victim lines. The exemplary embodiments described hereinare applicable to ADSL, ADSL2, VDSL2, SHDSL or any other DSL that couldbe affected by non-stationary crosstalk. The exemplary embodimentsdescribed herein provide for the use of the signal between two DSLmodems when they enter or leave an L2 or similar state to trigger theuse of these techniques.

The exemplary embodiments are applicable to determine when L2 modeshould be disabled on a particular line that is affecting other lineswith non-stationary crosstalk because the invention is unable tocompensate for the effect of such crosstalk on the victim lines. Forinstance, the exemplary embodiments described herein can monitor of thestability of a DSL connection, by examining coding errors and SNR marginon the received modem of modems victimized by non-stationary crosstalkfrom a particular line entering L2 mode.

The exemplary embodiments can perform vectoring in the downstreamdirection, such as from the central office or remote terminal toward thecustomer, whereby transmitters apply pre-coding to adjust thetransmitted symbols to minimize the effects of crosstalk into the otherlines. The transmitter pre-coding can adjust various characteristics ofthe signal, including the amplitude-vs-frequency and phase-vs-frequency,to minimize the effects of crosstalk to the other lines. The exemplaryembodiments can also perform vectoring in the upstream direction, suchas from the customer premises towards the central office or remoteterminal, whereby the effects of crosstalk are compensated from victimlines in the DSL receiver using knowledge of crosstalk coupling betweenlines and information, such as amplitude-vs-frequency andphase-vs-frequency of the mutually interfering DSL lines.

Upon reviewing the aforementioned embodiments, it would be evident to anartisan with ordinary skill in the art that said embodiments can bemodified, reduced, or enhanced without departing from the scope andspirit of the claims described below. For example, the techniques of theexemplary embodiments can be used in other situations wherenon-stationary crosstalk is induced in other DSL lines in a cable by aDSL connection. For instance, the exemplary embodiments are applicableto DSL modem pairs that go into a state that has a special PSD which ischaracteristic of the state, where the PSD of the transmitting modem inthe special state is characterized and the characteristics are known toboth modems in the connection due to the fact the modems are capable ofsignaling each other that the modems are in the special state. Asanother example, the exemplary embodiments are applicable to DSL modempairs that go into a state where entry into and out of the state occursrelatively frequently and with a difficult to characterize frequency sothat the changes in the transmitted signal's PSD induces non-stationarycrosstalk in other DSL lines in the cable. These situations can occur ina number of situations with both standard and proprietary DSLimplementations. For example, the exemplary embodiments are applicableto the ‘SOS’ rapid change of aggregate bit-rate described in ITU-T SG15/Q 4 contributions, and specified in Amendment 3 to ITU-T G.993.2. The‘SOS’ modes are designed to allow a pair of DSL modems to rapidly adaptto changes in the noise environment on the line. In order to utilize anSOS mode the pair of modems making up a DSL connection pre-negotiate oneor more configurations of bit loading, fine-gains, and TSS values whichcan be substituted rapidly for the configuration which the pair hasconfigured for normal operation. Should a period of noise on the lineoccur, such as that produced by electrical noise, such as an electricmotor starting at the customer's premises, which disrupts the DSL framesfor the normal configuration, the modems communicate with each otherover a robust internal communication channel as to which of thepre-negotiated substitute SOS configuration is to be used to maintainthe connection under the degraded conditions. The modems then use thechosen pre-negotiated configuration immediately. Although the DSL linessync rate will be lower when an SOS mode is invoked, it will continue tooperate, as the pre-negotiated SOS configuration is one where thetransmission characteristics more closely match the noise conditionscurrently on the line. When the period of increased noise ends, themodems will share information over the robust internal communicationschannel and can revert to the original higher rate configuration of theDSL connection. Since the SOS configurations on a line have differentconfigurations of the DMT tones from the normal operating configurationfor the connection, the PSD on the line at various frequencies may bedifferent between the normal configuration and an SOS configuration.This change results in fluctuating crosstalk radiated into other linesin the cable or cable/binder both when the SOS mode is initiated andwhen it is terminated. As the SOS modes are meant to be initiated andterminated very rapidly in order to preserve as much data capacity on aDSL connection as possible, the fluctuations in crosstalk into otherlines can also occur rapidly. Unlike the L2 power savings mode which istriggered by a period where there is no application data to transmitover the DSL connection, SOS modes occur during normal transport ofapplication data but where noise affects the Physical Layer of the DSLconnection and renders it temporarily unfit to transmit the applicationdata at the originally configured Physical Layer sync rate. Howeverentering or leaving SOS shares with entering or leaving L2 the followingtwo qualities. First entering or leaving an SOS configuration willrapidly change the crosstalk effects into other lines in thecable/binder. Second, the characteristics of the new configuration, andthus its PSD and effect on other lines in the cable/binder is known inadvance to both the transmitting and receiving modem. Because of thesetwo characteristics, the techniques described for this invention or usedwith L2 mode can be readily adapted by one skilled in the art to SOSmodes to ameliorate the effect of the changing crosstalk caused by a DSLline entering an SOS mode.

The present disclosure contemplates applying other techniques incombination with the vectoring techniques described herein, includingsetting the Signal to Noise Ratio Margin, the transmit Power SpectralDensity (PSD), and/or the allocation of power and bits among the DMTtones that make up the DSL signal, such that the receiver can withstanda potential increase of the noise. The exemplary embodiments alsocontemplate providing the receivers with adaptive mechanisms formonitoring the noise and for responding to noise changes such as On-LineReconfiguration operations, including bit-swapping.

Other suitable modifications can be applied to the present disclosurewithout departing from the scope of the claims below. Accordingly, thereader is directed to the claims section for a fuller understanding ofthe breadth and scope of the present disclosure.

FIG. 13 depicts an illustrative diagrammatic representation of a machinein the form of a computer system 1300 within which a set ofinstructions, when executed, may cause the machine to perform any one ormore of the methodologies discussed above. In some embodiments, themachine operates as a standalone device. In some embodiments, themachine may be connected (using a network) to other machines. In anetworked deployment, the machine may operate in the capacity of aserver or a client user machine in server-client user networkenvironment, or as a peer machine in a peer-to-peer (or distributed)network environment.

The machine may comprise a server computer, a client user computer, apersonal computer (PC), a tablet PC, a laptop computer, a desktopcomputer, a control system, a network router, switch or bridge, or anymachine capable of executing a set of instructions (sequential orotherwise) that specify actions to be taken by that machine. It will beunderstood that a device of the present disclosure includes broadly anyelectronic device that provides voice, video or data communication.Further, while a single machine is illustrated, the term “machine” shallalso be taken to include any collection of machines that individually orjointly execute a set (or multiple sets) of instructions to perform anyone or more of the methodologies discussed herein.

The computer system 1300 may include a processor 1302 (such as a centralprocessing unit (CPU)), a graphics processing unit (GPU, or both), amain memory 1304 and a static memory 1306, which communicate with eachother via a bus 1308. The computer system 1300 may further include avideo display unit 1310 (such as a liquid crystal display (LCD)), a flatpanel, a solid state display, or a cathode ray tube (CRT)). The computersystem 1300 may include an input device 1312 (such as a keyboard), acursor control device 1314 (such as a mouse), a disk drive unit 1316, asignal generation device 1318 (such as a speaker or remote control) anda network interface device 1320.

The disk drive unit 1316 may include a computer-readable medium 1322 onwhich is stored one or more sets of instructions (such as software 1324)embodying any one or more of the methodologies or functions describedherein, including those methods illustrated above. The instructions 1324may also reside, completely or at least partially, within the mainmemory 1304, the static memory 1306, and/or within the processor 1302during execution thereof by the computer system 1300. The main memory1304 and the processor 1302 also may constitute computer-readable media.

Dedicated hardware implementations including, but not limited to,application specific integrated circuits, programmable logic arrays andother hardware devices can likewise be constructed to implement themethods described herein. Applications that may include the apparatusand systems of various embodiments broadly include a variety ofelectronic and computer systems. Some embodiments implement functions intwo or more specific interconnected hardware modules or devices withrelated control and data signals communicated between and through themodules, or as portions of an application-specific integrated circuit.Thus, the example system is applicable to software, firmware, andhardware implementations.

In accordance with various embodiments of the present disclosure, themethods described herein are intended for operation as software programsrunning on a computer processor. Furthermore, software implementationscan include, but not limited to, distributed processing orcomponent/object distributed processing, parallel processing, or virtualmachine processing can also be constructed to implement the methodsdescribed herein.

The present disclosure contemplates a machine readable medium containinginstructions 1324, or that which receives and executes instructions 1324from a propagated signal so that a device connected to a networkenvironment 1326 can send or receive voice, video or data, and tocommunicate over the network 1326 using the instructions 1324. Theinstructions 1324 may further be transmitted or received over a network1326 via the network interface device 1320.

While the computer-readable medium 1322 is shown in an exampleembodiment to be a single medium, the term “computer-readable medium”should be taken to include a single medium or multiple media (such as acentralized or distributed database, and/or associated caches andservers) that store the one or more sets of instructions. The term“computer-readable medium” shall also be taken to include any mediumthat is capable of storing, encoding or carrying a set of instructionsfor execution by the machine and that cause the machine to perform anyone or more of the methodologies of the present disclosure.

The term “computer-readable medium” shall accordingly be taken toinclude, but not be limited to: solid-state memories such as a memorycard or other package that houses one or more read-only (non-volatile)memories, random access memories, or other re-writable (volatile)memories; magneto-optical or optical medium such as a disk or tape;and/or a digital file attachment to e-mail or other self-containedinformation archive or set of archives is considered a distributionmedium equivalent to a tangible storage medium. Accordingly, thedisclosure is considered to include any one or more of acomputer-readable medium or a distribution medium, as listed herein andincluding art-recognized equivalents and successor media, in which thesoftware implementations herein are stored.

Although the present specification describes components and functionsimplemented in the embodiments with reference to particular standardsand protocols, the disclosure is not limited to such standards andprotocols. Each of the standards for Internet and other packet switchednetwork transmission (such as TCP/IP, UDP/IP, HTML, HTTP) representexamples of the state of the art. Such standards are periodicallysuperseded by faster or more efficient equivalents having essentiallythe same functions. Accordingly, replacement standards and protocolshaving the same functions are considered equivalents.

The illustrations of embodiments described herein are intended toprovide a general understanding of the structure of various embodiments,and they are not intended to serve as a complete description of all theelements and features of apparatus and systems that might make use ofthe structures described herein. Many other embodiments will be apparentto those of skill in the art upon reviewing the above description. Otherembodiments may be utilized and derived therefrom, such that structuraland logical substitutions and changes may be made without departing fromthe scope of this disclosure. Figures are also merely representationaland may not be drawn to scale. Certain proportions thereof may beexaggerated, while others may be minimized. Accordingly, thespecification and drawings are to be regarded in an illustrative ratherthan a restrictive sense.

Such embodiments of the inventive subject matter may be referred toherein, individually and/or collectively, by the term “invention” merelyfor convenience and without intending to voluntarily limit the scope ofthis application to any single invention or inventive concept if morethan one is in fact disclosed. Thus, although specific embodiments havebeen illustrated and described herein, it should be appreciated that anyarrangement calculated to achieve the same purpose may be substitutedfor the specific embodiments shown. This disclosure is intended to coverany and all adaptations or variations of various embodiments.Combinations of the above embodiments, and other embodiments notspecifically described herein, will be apparent to those of skill in theart upon reviewing the above description.

The Abstract of the Disclosure is provided to comply with 37 C.F.R.§1.72(b), requiring an abstract that will allow the reader to quicklyascertain the nature of the technical disclosure. It is submitted withthe understanding that it will not be used to interpret or limit thescope or meaning of the claims. In addition, in the foregoing DetailedDescription, it can be seen that various features are grouped togetherin a single embodiment for the purpose of streamlining the disclosure.This method of disclosure is not to be interpreted as reflecting anintention that the claimed embodiments require more features than areexpressly recited in each claim. Rather, as the following claimsreflect, inventive subject matter lies in less than all features of asingle disclosed embodiment. Thus the following claims are herebyincorporated into the Detailed Description, with each claim standing onits own as a separately claimed subject matter.

What is claimed is:
 1. A non-transitory computer-readable storagemedium, comprising computer instructions which, responsive to beingexecuted by a processor, cause the processor to perform operationscomprising: monitoring a plurality of modems in a digital subscriberline system for transitioning between a full power mode and anothermode; determining crosstalk coupling characteristics between a pluralityof lines of the digital subscriber line system connected to theplurality of modems based on changes in amplitude of transmittedsignals, wherein the amplitude changes result from the transitioningbetween the full power mode and the other mode, wherein a change in atransmitted signal amplitude that results from multiple transitionsbetween the full power and other modes of a modem of the plurality ofmodems is utilized as a probing signal for the determining of thecrosstalk coupling characteristics between pairs of lines of theplurality of lines, wherein the crosstalk coupling characteristics aredetermined based on the change in the transmitted signal amplitude andare not determined based on monitoring changes to signal-to-noiseratio-vs-frequency information associated with other lines of theplurality of lines; and providing the crosstalk coupling characteristicsto at least some of the plurality of modems for performance ofpre-coding a transmitted signal, wherein the pre-coding is performedbased on the crosstalk coupling characteristics and temporalcharacteristics associated with the other mode, wherein the pre-codingof the transmitted signal reduces effects of fluctuating crosstalk, andwherein the pre-coding utilizes a multiple-input multiple-output channeltransfer matrix.
 2. The non-transitory computer-readable storage mediumof claim 1, wherein the plurality of lines are associated with a cable,and wherein the operations further comprise selecting some of theplurality of lines of the cable for performance of the pre-coding of thetransmitted signal and the processing of the received signal, whereinthe selecting is based on lines with a greatest crosstalk coupling andfrequencies with a greatest crosstalk coupling, and wherein theproviding of the crosstalk coupling characteristics to the at least someof the plurality of modems enables processing a received signal along aline of the plurality of lines, wherein the processing is performedbased on the crosstalk coupling characteristics and the temporalcharacteristics associated with the other mode, and wherein theprocessing of the received signal reduces effects of fluctuatingcrosstalk.
 3. The non-transitory computer-readable storage medium ofclaim 1, wherein the pre-coding of the transmitted signal is for atransmission during the other mode, the other mode being selected from agroup consisting of a low power mode and a save our showtime mode, andwherein the operations further comprise providing instructions foradjusting settings for a transmit power spectral density and anallocation of power and bits among tones of the transmitted signal,wherein the adjusting is based on a noise threshold.
 4. Thenon-transitory computer-readable storage medium of claim 1, wherein theoperations further comprise monitoring for a reduction in fluctuatingcrosstalk for the digital subscriber line system and disabling the othermode for a group of modems of the plurality of modems based on anidentification of the reduction, wherein the pre-coding is according toY=H*X+N, wherein Y is a received data vector, wherein H is themultiple-input multiple-output channel transfer matrix, wherein X is avector of channel inputs, and wherein N is a channel noise vector. 5.The non-transitory computer-readable storage medium of claim 4, whereinthe monitoring of the reduction of fluctuating crosstalk is based oncoding errors associated with a receiving modem of the plurality ofmoderns that is receiving the received signal.
 6. An apparatuscomprising: a memory to store computer instructions; and a controllercoupled with the memory, wherein the controller, responsive to executingthe computer instructions, performs operations comprising: determiningcrosstalk coupling characteristics between a plurality of lines of adigital subscriber line system connected to a plurality of modems,wherein a change in a transmitted signal amplitude that results frommultiple transitions between a full power mode and another mode of amodem of the plurality of modems is utilized as a probing signal for thedetermining of the crosstalk coupling characteristics between pairs oflines of the plurality of lines, wherein the crosstalk couplingcharacteristics are determined based on the change in the transmittedsignal amplitude and are not determined based on monitoring changes tosignal-to-noise ratio-vs-frequency information associated with otherlines of the plurality of lines; and providing the crosstalk couplingcharacteristics to the modem of the plurality of modems for performanceof pre-coding a transmitted signal, the pre-coding being performed basedon the crosstalk coupling characteristics, wherein the pre-coding of thetransmitted signal reduces effects of fluctuating crosstalk, and whereinthe pre-coding is based on quadrature amplitude modulation constellationpoints.
 7. The apparatus of claim 6, wherein the operations furthercomprise: monitoring the plurality of modems in the digital subscriberline system for transitioning between the full power mode and the othermode, wherein the providing of the crosstalk coupling characteristics tothe modem of the plurality of modems enables processing a receivedsignal along a line of the plurality of lines, the processing beingperformed based on the crosstalk coupling characteristics, wherein theprocessing of the received signal reduces effects of fluctuatingcrosstalk.
 8. The apparatus of claim 7, wherein the pre-coding andprocessing is further performed based on temporal characteristicsassociated with the other mode, and wherein the operations furthercomprise performing L2 mode scaling of the transmitted signal prior tothe pre-coding.
 9. The apparatus of claim 7, wherein the plurality oflines are associated with a cable, and wherein the controller selectssome of the plurality of lines of the cable for performance of thepre-coding of the transmitted signal or the processing of the receivedsignal, wherein the controller selects the some of the plurality oflines based on lines with a greatest crosstalk coupling and frequencieswith a greatest crosstalk coupling.
 10. The apparatus of claim 7,wherein the pre-coding of the transmitted signal is for a transmissionduring the other mode, the other mode being selected from a groupconsisting of a lower power mode and a save our showtime mode.
 11. Theapparatus of claim 7, wherein the controller monitors for a reduction influctuating crosstalk for the digital subscriber line system anddisabling the other mode for some of the modems of the plurality ofmodems based on a detection of the reduction.
 12. The apparatus of claim11, wherein the monitoring for the reduction of fluctuating crosstalk isbased on coding errors.
 13. The apparatus of claim 7, wherein theapparatus is implemented as a network device of a digital subscriberline system.
 14. A network device of a digital subscriber line system,the network device comprising: a memory to store computer instructions;and a controller coupled with the memory, wherein the controller,responsive to executing the computer instructions, performs operationscomprising: transitioning between a full power mode and another mode;receiving crosstalk coupling characteristics associated with a pluralityof lines of the digital subscriber line system, the network device beingconnected to a line of the plurality of lines, wherein a change in atransmitted signal amplitude that results from multiple transitionsbetween the full power mode and the other mode is utilized as a probingsignal for determining the crosstalk coupling characteristics;performing L2 mode scaling of a signal to be transmitted; and performingpre-coding of the signal to be transmitted, the pre-coding beingperformed based on the crosstalk coupling characteristics, wherein thepre-coding of the transmitted signal reduces effects of fluctuatingcrosstalk, wherein the pre-coding is based on quadrature amplitudemodulation constellation points, and wherein the performing of the L2mode scaling is prior to the pre-coding.
 15. The network device of claim14, wherein the pre-coding is further performed based on temporalcharacteristics associated with the other mode, wherein the crosstalkcoupling characteristics are determined based on the change in thetransmitted signal amplitude and are not determined based on monitoringchanges to signal-to-noise ratio-vs-frequency information associatedwith other lines of the plurality of lines.
 16. The network device ofclaim 14, wherein the plurality of lines are associated with a cable,and wherein a portion of the plurality of lines of the cable is selectedfor performance of the pre-coding of the transmitted signal, and whereinsettings for a transmit power spectral density, a signal-to-noise ratiomargin, and an allocation of power and bits among tones of thetransmitted signal are adjusted based on a noise threshold.
 17. Thenetwork device of claim 16, wherein the portion of the plurality oflines is selected based on lines with a greatest crosstalk coupling andfrequencies with a greatest crosstalk coupling.
 18. The network deviceof claim 14, wherein the pre-coding of the transmitted signal is for atransmission during the other mode, the other mode being selected from agroup consisting of a lower power mode and a save our showtime mode. 19.A method, comprising: monitoring, by a processor, a plurality of linesin a digital subscriber line system, the plurality of lines beingconnected to modems, wherein fluctuating crosstalk occurs in theplurality of lines based on at least a portion of the plurality of linestransitioning between a full power mode and other modes; determiningcrosstalk coupling characteristics associated with the plurality oflines, wherein a change in a transmitted signal amplitude that resultsfrom multiple transitions between the full power mode and the othermodes is utilized as a probing signal for determining the crosstalkcoupling characteristics, wherein the crosstalk coupling characteristicsare determined based on the change in the transmitted signal amplitudeand are not determined based on monitoring changes to signal-to-noiseratio-vs-frequency information associated with other lines of theplurality of lines; and applying, by the processor, vectoring to linesof the plurality of lines to reduce effects of the fluctuating crosstalkbeing experienced by the plurality of lines, wherein the applying of thevectoring is by pre-coding a transmitted signal utilizing amultiple-input multiple-output channel transfer matrix.
 20. The methodof claim 19, comprising: applying the vectoring by processing a receivedsignal along the lines, the pre-coding and processing being performedbased on the crosstalk coupling characteristics and temporalcharacteristics associated with the other mode.
 21. The method of claim19, wherein a portion of the plurality of lines is selected forreceiving the crosstalk coupling characteristics based on lines with agreatest crosstalk coupling and frequencies with a greatest crosstalkcoupling, wherein the pre-coding is according to Y=H*X+N, wherein Y is areceived data vector, wherein H is the multiple-input multiple-outputchannel transfer matrix, wherein X is a vector of channel inputs, andwherein N is a channel noise vector.
 22. The method of claim 20, whereinthe pre-coding of the transmitted signal is for a transmission duringthe other modes, the other modes being selected from a group consistingof a lower power mode and a save our showtime mode.